PGS Mathematics: Guesstimation, A Pumpkin Purchasing Guide

Here’s a great post courtesy of our Math Editor, Vickie Kearn with special thanks to authors Larry Weinstein and John Adam.


It is almost Halloween and if you haven’t bought a pumpkin yet, here is a handy guide to help you pick out the perfect one—that would be the largest one you can actually afford (and pick up without a forklift.)

This pumpkin is of course priceless…

Guesstimation method

Since you probably won’t have too many tools with you in the pumpkin patch, I recommend this approach: A gallon of milk is about the same shape as your average pumpkin and it weighs 8 pounds.  So, all you have to do is decide about how many gallons of milk your pumpkin is equal to and multiply by 8. You need to remember that a pumpkin is filled with a lot of low-density seeds and pulp and the skin is only an inch or so thick. I suggest that you divide your total by 2 to account for these factors. If your pumpkin is smaller than a gallon of milk you will need to be a little clever. (I doubt this is necessary since you should be able to pick up and pay for something this small!) Now that you know the weight of your pumpkin, you will know whether or not you can carry it to the car. Now, multiply the number of pounds by the price per pound and you will know whether or not you can afford it.

More precise method

If the pumpkin you are considering is really big, you might prefer this method.  You will need a tape measure or a piece of string (and some Guesstimation skills) to measure your pumpkin. Measure the circumference of the pumpkin at its widest part. Next, measure from the ground over the top of the pumpkin to the ground again. Do this for both the long and short sides of the pumpkin. Now, add your three numbers together.  Find your number in the chart below and you will have a very good estimate of how much your pumpkin weighs. Now you can go back to the final steps under the Guesstimation method.

Thanks to Larry Weinstein and John Adam for the Guesstimation approach. If you like to Guesstimate, you will want to read Guesstimation: Solving the World’s Problems on the Back of a Cocktail Napkin.   You might also enjoy Question 32 in A Mathematical Nature Walk by John Adam.  It is the super scientific method for pumpkin weighing.

The table (above) used for the “more scientific method” was developed by David Martin from Little Britain, Ontario using multiple regression analysis. This method is further explained at

Happy picking from your friends at PUP!

Special thanks to jacket designer Jason Alejandro for allowing us to use the lovely image of his daughter in this post.